IP Address Classes (CCNA)

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IP Address Classes

 

Class A:

  • The 1st bit of the 1st octet is static and is 0
  • 1st 8 bits are network bits and the rest 24 bits are host bits.
  • Subnet mask is 255.0.0.0
  • Host portion and network portion can’t be all 0’s and 1’s
  • Class A IP address range = 0-127
  • of networks = 27-2 = 126
  • of Hosts = 224-2 = 16777144

Class A exceptions:

  • 0.0.0= Default network
  • 0.0.0 = Loopback purpose

Class B:

  • The 1st two bits of the 1st octet are static and are 10
  • 1st 16 bits are network bits and rest 16 bits are host bits.
  • Subnet mask is 255.255.0.0
  • Host portion and network portion can’t be all 0’s and 1’s
  • Class B IP address range = 128-191
  • of networks = 214-2 = 16384
  • of Hosts = 216-2 = 65534

Class C:

  • The 1st three bits of the 1st octet are static and are 110
  • 1st 24 bits are network bits and rest 8 bits are host bits.
  • Subnet mask is 255.255.255.0
  • Host portion and network portion can’t be all 0’s and 1’s
  • Class C IP address range = 192-223
  • of networks = 221-2 = 2097152
  • of Hosts = 28-2 = 254

Class D:

  • The 1st four bits of the 1st octet are static and are 1110
  • Used for multicast purposes e.g RIP: 224.0.0.9
  • Class D IP address range = 224-239

Class E:

  • The 1st four bits of the 1st octet are static and are 1111
  • Reserved for experimental and future use.
  • Class E IP address range = 240-255

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